Portable, internal combustion powered tools, having various different means for respectively conducting or charging combustible fuels into their combustion chambers, and for exhausting combustion products out from their combustion chambers, are of course well-known in the industry. Examples of such portable, internal combustion powered tools are disclosed within U.S. Pat. No. 6,912,988 which issued to Adams on Jul. 5, 2005, U.S. Pat. No. 6,840,033 which issued to Adams on Jan. 11, 2005, U.S. Pat. No. 5,752,643 which issued to MacVicar et al. on May 19, 1998, U.S. Pat. No. 4,905,634 which issued to Veldman on Mar. 6, 1990, U.S. Pat. No. 4,759,318 which issued to Adams on Jul. 26, 1988, U.S. Pat. No. 4,665,868 which issued to Adams on May 19, 1987, U.S. Pat. No. 4,510,748 which issued to Adams on Apr. 16, 1985, and U.S. Pat. No. 4,365,471 which issued to Adams on Dec. 28, 1982. While the portable, internal combustion powered tools, disclosed within such aforenoted patents, are operationally satisfactory, it is desired to provide such portable, internal combustion powered tools with combustion chambers which are characterized by improved internal structural features that will, for example, enhance the mixing together of the air and fuel mixture components being introduced into the combustion chambers of the internal combustion powered tools, that will enhance the flow distribution of the air/fuel mixtures within and throughout the combustion chambers of the internal combustion powered tools, that will enhance the actual combustion of the air/fuel mixtures within and through-out the combustion chambers of the internal combustion powered tools, and that will enhance the efficiency of the exhausting, scavenging, or purging of the combustion products out from the combustion chambers of the internal combustion powered tools.
As has been noted, for example, within the aforenoted U.S. Pat. No. 6,912,988 which issued to Adams on Jul. 5, 2005, it is desirable to reduce the time period within which the entire combustion cycle is achieved, wherein the combustion cycle is defined between the time at which spark ignition occurs, when the peak pressure from the combustion of the air/fuel mixture within the combustion chamber is obtained so as to drive a power piston in order to drive a fastener through the power tool, in order to discharge the fastener out from the power tool, and to insert or imbed the fastener into a substrate, and when the exhausting, scavenging, or purging of the combustion products out from the combustion chamber of the power tool is completed. More particularly, it is desirable to achieve rapid combustion of the air/fuel mixture within the combustion chamber of a power tool in order to facilitate a faster operation of the power tool as defined between the time when the operator pulls the trigger and when the fastener is driven through the power tool, discharged from the power tool, and inserted or embedded into a substrate. Reduction of the time period, within which the combustion process is achieved, also facilitates the development of peak combustion pressures within the combustion chamber whereby such peak pressures will impact the power piston so as to achieve high velocity movement of the power piston in order to successively drive the fastener through the power tool, to discharge the fastener out from the power tool, and to insert or embed the fastener into a substrate.
One way of achieving higher burn rates or more rapid combustion of the air/fuel mixture within the combustion chamber of an internal combustion powered tool is to induce turbulence of the air/fuel mixture within and throughout the combustion chamber. Such turbulence is known to not only effectively shorten the time period at which peak pressures are obtained subsequent to ignition, but in addition, to enhance or boost the peak pressures of the combusted air/fuel mixtures. In addition, higher peak combustion pressures can also be achieved from the combustion of a predetermined amount of fuel, mixed with air at a predetermined stoichiometric ratio, and at a predetermined compression ratio, by effectively lengthening the combustion chamber as a result of dividing the combustion chamber into a pre-combustion chamber and a main combustion chamber, and subsequently igniting the air-fuel mixtures, disposed within the pre-combustion and main combustion chambers, in sequence. For example, a spark igniter is conventionally located at one end of the pre-combustion chamber which is remote from the main combustion chamber, and subsequently, the spark igniter ignites the air/fuel mixture present within the pre-combustion chamber. A flame front, which is formed at the end of the pre-combustion chamber that is located remote from the main combustion chamber, propagates toward the main combustion chamber, and pushes a portion of the air/fuel mixture, disposed within the pre-combustion chamber, into the main combustion chamber in advance of the arrival of the flame front from the pre-combustion chamber into the main combustion chamber. Both turbulence and increased pressure are created within the air/fuel mixture disposed within the main combustion chamber wherein the air/fuel mixture, disposed within the main combustion chamber, is subsequently ignited upon arrival of the flame front into the main combustion chamber.
As has been further noted, for example, within the aforenoted U.S. Pat. No. 6,840,033 which issued to Adams on Jan. 11, 2005, the use of curved pre-combustion chambers is believed to increase flame-front propagation speed and to shorten the time required to achieve peak combustion pressure subsequent to ignition, as compared to the use of linear or straight pre-combustion chambers having the same or similar cross-sectional dimensions. It is also to be appreciated, however, that peak combustion pressure is a function of the volume of the air/fuel mixture within the combustion chamber, and accordingly, combustion chambers characterized by increased length dimensions, which obviously increase the overall volume of the combustion chambers, can adversely affect the development of the peak combustion pressure in that the flame fronts must traverse greater combustion chamber lengths in order to develop the desired peak combustion pressures. Still yet further, combustion efficiency is also a function of, or depends upon, the quality of the air/fuel mixture disposed within the combustion chamber. Between each firing cycle, exhaust gases or combustion products must be removed from the combustion chamber and a fresh charge of the air/fuel mixture must be introduced into the combustion chamber. It is therefore imperative to remove as much of the exhaust gases or combustion products, generated during the previous tool firing cycle, as is possible in order to degrade the incoming fresh charge of the air fuel mixture as little as possible whereby the new or fresh incoming air/fuel mixture, in preparation for the new or subsequent tool firing cycle, will be characterized by means of the highest possible quality.
A need therefore exists in the art for a new and improved combustion chamber system, for use within an internal combustion powered fastener-driving tool, wherein the combustion chamber system would be able to provide good mixing or turbulence characteristics in connection with the air/fuel mixture charged into and distributed throughout the combustion chamber system, wherein, despite the fact that the combustion chamber system would provide or define a combustion chamber characterized by relatively large length dimensions, the combustion chamber system would also be characterized by increased air/fuel mixture distribution and ignition efficiency by effectively causing the air/fuel mixture to be divided into multiple flame fronts which only need to traverse relatively shortened distances before complete combustion, and the development of peak combustion pressures, occur so as to achieve high velocity movement of the power piston which is adapted to impact upon the fastener to be driven through and discharged from the power tool, and wherein the combustion chamber system would be characterized by enhanced exhaust gas or combustion product scavenging or purging techniques in order to enhance the quality of a new or fresh air/fuel mixture charged into the combustion chamber.